I have three HS220 dimmer switches. All have been working wonderfully using the dimmable LED bulbs that were installed prior to the switches. I guess I just got lucky.
I've just changed the dimmable bulbs in one of the light fixtures served by one of the HS220 switches. On doing so I also performed the dimmer calibration so that the lights will come on visibly (albeit very dim) when the dimmer is at 1%. I did the same for all the switch & bulb combinations when I first installed the switches.
The new bulbs that I have chosen for this 5-bulb fixture are the Sylvania TruWave Dimmable A19 Clear Soft White bulbs in the 40W equivalent variety (actually 5.5W). In the fixture and on the HS220, the bulbs do not flicker. They dim properly and otherwise work beautifully. The only bug with using these bulbs with this dimmer is that when the brightness reaches 100%, they blink, just once, and then stay on. If I leave the brigthess at anything less than 100% (I can do 95% in the app or 88% on the wall switch), then turning them off and on again produces no blink. If I raise the brigthness to 100% by any means (switch or app), then they blink once and stay on. Every power-on from any control produces the quick ramp up and when they return to 100% - the single blink.
If there were a way to calibrate the dimmer with a maximum output (in the same fashion that you can calibrate its minimum output), then the issue of the blink at 100 could be avoided. To the eye, 95% and 100% are indistinguishable.
I've called tech support and the answer I received was the bulbs are not compatible with the dimmer, and that there is no way to govern the max output on the dimmer.
I'm posting this here in case anyone finds a suitable means to permanently avoid the blink, or better yet, for Kasa engineers to see and provide a calibration option to set a max output (which might also be desirable for folks with 100W equivalent bulbs that they'd rather not ever see at max brightness).